New modem – do I need to change drivers?

Currently I have a generic 33.6 external modem on a system and the modem is not always functioning corectly. I would like to replace it with another external. Do I need to change the drivers for the new modem to work or it I keep the ports and everything the same will the new modem just work? Do I need to stay with 33.6 and should I get Hayes or any brand?